Arawhata Constructed Wetland Complex
Water from multiple sources in the Arawhata catchment current flows onto the site of the wetland complex. That water contains nitrogen, sediment and phosphorus which contributes to poor water quality in Punahau Lake Horowhenua.
The Arawhata Constructed Wetland Complex will help to reduce the concentrations of nitrogen, sediment and phosphorus within the water. This, combined with the other interventions within the catchment and the lake itself, will improve the water quality within Punahau.
What is involved?
The wetland site is located approximately 3km west Taitoko Levin, 6km from the sea (Hōkio Beach), and located between Punahau and Lake Waiwiri. The site is accessed via Hōkio Beach Road near the north-east side of the site. The proposed wetland site has previously operated as a 142ha dairy farm.
The concept design for the Arawhata Constructed Wetland Complex includes a master plan, with construction split into three phases. The first phase aims to convert at least 15 hectares of farmland into a constructed wetland complex by December 2026. The constructed wetland complex will incorporate plants historically found in this area prior to its clearance, species such as harakeke (flax), carex, and rushes.
A Wetland Design Group and a Mātauranga Rōpu (Kāhui Ārahi) have been established to develop the wetland. A Community Stakeholder Group has also been formed, with input from this group to be considered in the process.
How is it funded?
The wetland complex project was boosted by the Mahi mō te Taiao – Jobs for Nature Horowhenua (Waiopehu) Freshwater Management Unit Water Quality Interventions project (2021-2024). This support comes from Central Government funding and is complemented by Horizons Regional Council (a total of $12.5 million; $11.2 million from Central Government and $1.3 million from Horizons).
As further funding becomes available the second and third construction phases will be considered. These phases will extend the constructed wetland complex with new drains, bunds, planting and a walking trail through the wetland.
Fast-track consenting process
We were granted consent via the fast-track consenting process to construct and maintain the Arawhata wetland. You can learn more about this process and read supporting information on the Environmental Protection Authority website.
Stage One
Stage One of the project is underway. This stage involves constructing sediment basins, modifications to existing drainage systems on the site, deepening and widening of other drains, and planting of native plants.
Plants for the wetland will be eco-sourced (sourced locally), with iwi input for the final selection of species. The preference is for species historically found across the project site, such as those in surrounding areas like the Arawhata bush block and Waiwiri Reserve, and within the ecological district.
The land at the wetland site not affected by Stage One construction will continue to be farmed in some capacity until Stage Two and Stage Three are completed. However, changes have already been made. From June 2023 the farm was no longer a dairy farm. Data shows purely changing the land use has already reduced the level of nutrients that are leaching from the property. The land is now being utilised for dry stock and a cut-and-carry farm system.